1. Field of Invention
The present invention relates to a pneumatic motor and, more particularly, to a pneumatic motor that is small in size, easy in fabrication and low in cost.
2. Related Prior Art
Referring to FIGS. 1 through 8, a conventional pneumatic motor includes a shell 10, two covers 20 located in the shell 10, a cylinder 30 located between the covers 20 and a rotor 40 located on the covers 20.
Referring to FIG. 8, the shell 10 defines a space 15 for containing the other elements, two inlets 17 defined in the wall of the space 15 and an outlet 16 defined in an internal side of the wall of the space 15.
Referring to FIGS. 2 and 3, each of the covers 20 defines a central aperture 21, two arched channels 23 in an internal side, two recesses 24 in the internal side and two radial channels 22 for communicating each of the arched channels 23 with a related one of the recesses 24.
Referring to FIGS. 4 and 5, the cylinder 30 defines an eccentric space 31 for receiving the rotor 40. The wall of the eccentric space 31 (or the cylinder 30) includes a thick portion and a thin portion opposite to the thick portion. Two inlets 32 are defined in the thick portion of the cylinder 30. Two apertures 33 are defined in an end of the thick portion of the cylinder 30. Two cavities 34 are defined in an external side of the thick portion of the cylinder 30. Each of the cavities 34 communicates a related one of the inlets 32 with a related one of the apertures 33. A plurality of outlets 35 is defined in the thin portion of the cylinder 30.
The rotor 40 includes two shafts 41 each extending from an end and a plurality of grooves 42 longitudinally defined in the periphery. A fin 45 is movably disposed in each of the grooves 42.
Referring to FIG. 6, the rotor 40 is disposed in the eccentric space 31 of the cylinder 30. Each of the shafts 41 is inserted in the aperture 21 of a related one of the covers 20. The covers 20 are attached to the cylinder 30. The cylinder 30 is disposed in the shell 10.
Referring to FIGS. 7 and 8, pressurized air travels into the cavities 34 from the inlets 17. A first portion of the pressurized air travels into the space 31 through the inlets 32 while a second portion of the pressurized air travels into the recesses 24 through the apertures 33. From the recesses 24, the second portion of the pressurized air travels into the arched channels 23 through the radial channels 22. Finally, the second portion of the pressurized air travels into the space 31 from the arched channels 23.
Some problems have been encountered in the fabrication and use of this conventional pneumatic motor. Firstly, the manufacturing is troublesome and expensive. This is partly because a lot of apertures, channels, recesses and cavities are made. This is partly because high precision is required in casting the cylinder 30 while eccentrically making the eccentric space 31 in the cylinder 30. Secondly, the cylinder 30 is bulky and heavy for including the thick portion.
The present invention is therefore intended to obviate or at least alleviate the problems encountered in prior art.